Page 89 - eBook_Proceedings of the International Conference on Digital Manufacturing V2

Fabrication and Characterization of a Low-Cost Piezoelectric using Rochelle
Salt for Energy Harvesting and Sensor Applications

Researchers have shown that semi-solid-state processing
produce higher-quality castings with fewer defects by reducing
gas entrapment and shrinkage (Kapranos, 2019; Spencer,
Mehrabian & Flemings, 1972; Mallick, 2010; Jirková, Rubešová,
Jeníček, Hradil & Kučerová, 2022).

Another key advantage of SSMP is its energy efficiency. It
operates at a lower temperature compared to traditional fully
liquid casting. In regular casting, metal must be fully melted,
which uses a lot of energy. SSMP saves energy by only heating
the metal until it’s partly melted. This not only saves energy, but
also reduces thermal stress on moulds, extending their life and
lowering maintenance costs. The process also improves control,
as the semi-solid metal flows smoothly, reducing defects and
making the process more cost-effective and environmentally
friendly (Tajudin, Ahmad, Alias, Razak & Alang, 2023;
Kapranos, 2019; Husain, Ahmad & Rashidi, 2017, Deepak
Kumar, Mandal & Chakraborty, 2014; Omar, Sajuri, Mohamed &
Samat, 2018).

THIXOTROPIC BEHAVIOUR OF SSMP

The semi-solid state is characterised by its thixotropic behaviour,
meaning the material behaves like a fluid under shear stress but
maintains a solid-like structure when at rest. This property is
essential for processes like thixoforming and rheocasting,
facilitating better mould filling while maintaining structural
integrity and reducing defects compared to traditional casting
methods. Knowing the behaviour of thixotropic materials helps
improve the process because it affects how easily the metal flows
and how well it works. The thixotropic behaviour of semi-solid
metals can be attributed to three mechanisms: shear-thinning,
time-dependent viscosity, and thixotropic strength (Czerwinski,
2006; Alexandrou, Burgos & Entov, 1999; Megalingam, Ahmad,
Maarof & Sudhakar, 2022; Keung, Lee, Shan & Luo, 2008):

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